The past 72 hours have revealed this truth: This Ivy League-educated quarterback is one tough S.O.B., who might have saved the Jets’ season.

Todd Bowles declared after practice Wednesday that Fitzpatrick, who suffered a torn ligament in his left thumb in Oakland, will start against the Jaguars on Sunday. The coach would have likely done cartwheels if not for his recent partial knee replacement.

Although Fitzpatrick will have to live with constant pain until he eventually goes under the knife, the Jets appear to have avoided a crisis for the time being.

“There is relief there, because he’s led us this whole year,” wide receiver Brandon Marshall said. “We got off to a fast start. He’s done some great things for us. On and off the field, he’s a leader.”

Fitzpatrick practiced without incident Wednesday in a self-described “trial run” in his new reality. He wore a padded “special glove” to protect his thumb. Although the veteran stopped short of saying that the initial pain has subsided in subsequent days, he admitted that “it’s not really normal.”

“It’s painful enough to get me out of changing diapers,” said the father of five.

Fitzpatrick hasn’t exactly been a statistical giant (11 TDs, 7 INTs, 86.5 passer rating), but he is invaluable for a Top 10 offense that has leaned on his veteran leadership. The quarterback developed a connection with wide receivers Eric Decker and Marshall, which has had as much to do with the Jets’ offensive success as any other component. Keeping that continuity is pivotal for a 4-3 team at the crossroads.

“He’s done such a great job so far this year,” Decker said. “It’s hard when you got to make a change at that position, because there’s so much that goes into it. The chemistry between the skill players and the quarterback takes time.”

Fitzpatrick covers his injured left thumb with a glove Wednesday.

Geno Smith, who had an uneven performance in relief last week, understandably had conflicting emotions, but there’s no doubt that if anyone is going to help the Jets snap their four-year playoff drought, it’s going to be the guy with overgrown facial hair with a degree in economics and a love for the Rubik’s Cube (which will be challenging to solve now with only one healthy thumb).

“Obviously we’re praying that Fitz continues to get better…,” said Smith, who practiced fully despite a bruised left shoulder. “I understand what’s going on, but at the same time, you still want to play.”

Fitzpatrick consulted friend and former teammate Carson Palmer, who sent a text message to the Jets quarterback Sunday afternoon. Palmer, who suffered ligament damage to his left thumb a month into the 2009 season, offered tips to play through the injury. Palmer started every game that season after getting hurt in Week 5. He underwent surgery after the Bengals lost to the Jets in the playoffs.

“I don’t want to put the team in a position where I’m going to go out and hurt the team or turn the ball over or try to be a hero, because something is compromised,” Fitzpatrick said. “I want to help the team. If I can do that without putting me or the team in a compromising position, I will. And I think I will be able to do that.”

Fitzpatrick is still navigating through the logistics of playing without much help from his thumb. He’s already uncovered that his left thumb isn’t really involved in taking a snap under center. The glove will help with grip. Although Fitzpatrick admitted that “there’s some stuff that I’ll have to do differently,” any adjusted mechanics of playing the position don’t seem overwhelming.

Fitzpatrick has played through broken ribs in the past, but this physical discomfort might be a different beast. He said that he won’t take a cortisone shot.

“You have to have some sort of mental toughness about you to last this long in the league,” Marshall said.

It’s impossible to know how long the signal caller will be able to play with the pain. Can he power through for the next nine weeks… and beyond?

Fitzpatrick has been called just about everything in his 11 seasons. Now, there’s one adjective that is permanently off limits for the oft-criticized journeyman: soft.